The genus Liriodendron consists of two species of large deciduous trees. Liriodendron tulipifera is native to eastern North America, and L. chinense is native to China and Vietnam. Commonly called tulip poplar, Liriodendron is in the Magnolia family and is not a true poplar. It is sometimes called tulip magnolia, whitewood, tuliptree and yellow or white poplar.
The tree gets its name from its greenish-yellow flowers with orange markings that resemble a tulip at first glance. Upon closer inspection, similarities to the genus Magnolia will be apparent. Mature trees sometimes display pyramidal forms, but more typically tend to produce a broad, symmetrical columnar shape in open areas. Flowers form about 15 years after planting on trees started from seed. Plants propagated by cutting or by grafting from mature trees flower much faster, typically in two to three years. Large, multilobed leaves turn a striking gold in the fall. During drought they may prematurely turn yellow and defoliate. This stately tree prefers full to partial sun in deep, fertile, moist soils.
Characterized by rapid growth, tulip poplars range between 50 to 70 feet high, but can grow over 100 feet tall and 40 feet wide with trunk diameters up to 4 to 8 feet. This is not a tree for small landscapes, though a few cultivars are available for the typical small suburban year. L. tulipifera ‘Arnold’ is the same tree as ‘Fastigiatum’. Named after the Arnold Arboretum, ‘Arnold’ forms a neat, narrow, flat-topped column, maturing to 60 feet high and 20 feet wide. Well adapted to North Carolina (Zones 6 to 8), this cultivar may show a few problems, including narrow crotch angles, which can result in branch splitting, and leaf miners. Visitors to the JC Raulston Arboretum (JCRA) will find a specimen of ‘Arnold’ to the west of the McSwain Education Center.
L. tulipifera ‘Ardis’, the little leaf tulip poplar, is an excellent choice for compact landscapes. Reduced in both leaf size and stature, this tree can be spotted growing near the JCRA parking lot. Other compact forms of tulip tree have recently been discovered, so expect some new cultivars in a few years.